I'm looking for a tool that works across windows (xp through 7) that will allow me to open a TCP connection to a specified ip and port. This functionality used to exist in windows xp (netsh diag connect iphost ), but the Netsh diag commands seem to have been removed in vista/7. I've been looking around for something similar, and I've searched Super User, but I can't seem to find anything.

Something that's already built into windows would be ideal, but a small executable that does this (preferably command line, standalone executable).

Edit: I should have specified further. I'm familiar with Telnet and putty, and it is what I currently use, however, I'm in an environment where I have to guide non-technical users through troubleshooting very technical problems over the phone, without any form of remote access (sounds fun, right?). While telnet works, it doesn't explicitly state whether or not the TCP connection was successful; you have to look at the title bar and the contents of the terminal output, which, for some reason, seems to be impossible to users. I'm looking for something with a clear "TCP Connection completed successfully/failed" type response, if such a tool exists.

Edit #2: Thanks to everyone who answered. All suggestions were good, despite the fact that I didn't post as clear a question as I should have. Thanks for the help.

Thank you all. Most of these tools I'm very familiar with, and they're what I currently use, however, I'm looking for something that explicitly states it either successfully connected or failed in pretty plain text. Telnet requires you to look at the title of the window and the content of the output, all of which aren't easy to describe to non-technical users over the phone (no remote access). I should have specified this point earlier.
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TheEmpireNeverEndedFeb 21 '12 at 20:50

I'd like to test these further and see the output I get from NC and socat, but I can't at the moment thanks to the wonders of corporate firewalls.
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TheEmpireNeverEndedFeb 21 '12 at 21:16

I'm accepting this as the answer. Netcat is awesome. I haven't tested the windows version yet, but I played with nc on Fedora 16, and with the -v switch, it's pretty much exactly what I'm looking for.
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TheEmpireNeverEndedFeb 22 '12 at 15:06

I found most useful in a shell scripting scenario to use nc -v -w 5 <host> <port> as result output can be compiled and reported nicely. Adjust -w <timeout in secs> value to your environment (this applies to both reachable and non-reachable endpoints and limits the speed of scanning).
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JGurtzMay 20 '14 at 20:33

Just use Putty it's tiny (and has a portable app version). It lets you specify port and can use telnet which is a TCP connection. It also has other useful functions like serial connections (no hyper terminal in Windows 7), SSH, And Rlogin. It even has a RAW function that lets establish RAW TCP connections.

Also just so your aware: Telnet is included in XP, you can use it from the command line IE:

Telnet still comes with windows it is just not installed, however you do not need your windows install CD to install it, in fact just type pkgmgr /iu:"TelnetClient" and it will prompt you with a UAC dialog and it will will be installed.
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Scott ChamberlainFeb 21 '12 at 20:51